1. Field of the Invention
The present invention relates to an optical pickup device used for reproduction and recording from/into an optical disk such as CD (compact disk), DVD (digital versatile disk), etc., and a connection structure of flexible printed circuits used in optical pickup devices.
2. Description of the Related Art
Conventionally, a thin optical pickup device (having a thickness of at most 7 mm) used for reproduction and recording from/into an optical disk such as CD, DVD, etc., or an optical disk drive device with a thin optical pickup device incorporated therein is structured as shown in FIG. 8. Parts, such as laser diodes, various lenses, mirrors, photodetectors (not shown), etc., which constitute an optical system, are arranged on an optical pickup case 3 formed by means of die casting or molding, of which main components comprise metal such as Zn, Mg, Al, etc. and a PPS (polyphenylene sulfide) resin, and a flexible printed circuit 2 is used as means that supplies an electric signal. Accompanying with thinning of optical disk drive device, connectors cannot be used due to projection limitations. Therefore, the flexible printed circuit 2 is structured into an integral form to extend to a portion 8 thereof, which is inserted into a connector of a drive side.
FIG. 10 shows a state, in which an optical pickup device is assembled into an optical disk drive device. An optical pickup device body 1 has an objective lens 5 facing upwardly and the lens 5 is opposed to an optical disk (not shown) through a notched portion of a cover 9 of the drive. The optical pickup device performs information reading and writing while moving between an outer periphery and an inner periphery of the optical disk. All these parts are assembled into an optical disk drive device body 10 to provide a product.
In this manner, while a flexible printed circuit used in a thin optical pickup is structured in an integral form, portions arranged on an inner side and an outer side of the flexible printed circuit are different from each other in performance required originally, and high density is emphasized on the inner side and flexibility is emphasized on the outer side. Hereupon, means of solution in the flexible printed circuit 2 made into an integral form has been proposed to select a flexible printed circuit, which has optimum performances for high density and flexibility, as a method that meets both performances required of a portion of the flexible printed circuit to be fixed to an optical pickup device and a portion of the flexible printed circuit to be inserted into the connector of the drive.
Meanwhile, various parts cannot but be arranged at a high density in horizontal and vertical directions in a narrow optical pickup device, and therefore, a flexible printed circuit serving as signal transmission is required to assume a complex configuration. This requires a divided structure for a flexible printed circuit in terms of cost since necessary configurations obtained from a single original sheet cannot be increased in number and even a portion, for which a simple structure will do, is influenced by a portion, which takes longest time, because of different necessary processes according to portions.
In the meantime, the optical pickup device shown in FIG. 8, or an optical disk drive device, into which a thin optical pickup device is assembled, is assembled through a plurality of complex processes. Therefore, there often arises a case in which the optical pickup device or the optical disk drive device is deemed as defective products due to dents, defects, etc. generated in the flexible printed circuit during assembling process after a process, in which adjustment is accomplished on a light-emitting element, a photodetector, and various optical parts of the optical pickup device, is performed. By adopting division of a flexible printed circuit into a plural printed circuits and connection of flexible printed circuits, an increase in yield of products and reduction in cost can be realized (see, for example, Japanese Patent Application Laid-Open Publication Nos. 2005-276263 and 2006-245514).
Because of a projection limitation on an optical pickup, a connector proposed in Japanese Patent Application Laid-Open Publication No. 2006-310449 cannot be used for connection of two flexible printed circuits, and so the printed circuits are connected to each other by means of soldering. In case of adopting division of a flexible printed circuit and connection of flexible printed circuits shown in FIG. 9A, when a conductor pattern of a the first flexible printed circuit and a conductor pattern of a second flexible printed circuit are caused to face and overlap each other, the second flexible printed circuit is made to define a back surface and a connector side contact 8 is reversed. Hereupon, as shown in FIG. 9B, the connector side contact 8 is directed upward by connecting the other end of the first flexible printed circuit and the other end of the second flexible printed circuit so as to have them facing and overlapping each other, and bending the connected ends of the flexible printed circuits at 90° in a projection direction (vertical direction) of the optical pickup device, or fixing the connected end of the first flexible printed circuit and bending the connected end of the second flexible printed circuit at 180°.